Semiconductor circuitry

ABSTRACT

Semiconductor circuitry comprises a transistor pair ( 11, 12 ) consists of a transistor having a base electrode to which a first signal is applied, and another transistor having a base electrode to which a signal having a phase opposite to that of the first signal is applied, the collector electrodes of those transistors being connected to each other and the emitter electrodes of the transistors being connected to each other, a third transistor ( 13 ) connected between a common emitter of the transistor pair and a ground potential and having a base electrode to which a second signal is applied, an output load ( 51 ) connected between a common collector of the transistor pair and a power supply (Vcc), and an output circuit for furnishing a third signal from the common collector of the transistor pair, thereby suppressing generation of any even-order higher harmonic of a local oscillation signal when the semiconductor circuitry operates from a low voltage.

CROSS-REFERENCE TO THE RELATED APPLICATION

[0001] This application is a continuation of International ApplicationNo. PCT/JP99/03455, whose international filing date is Jun. 29, 1999,the disclosures of which Application are incorporated by referenceherein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to semiconductor circuitry. Moreparticularly, it relates to a frequency multiplier provided withtransistors for multiplying the frequencies of signals of ahigh-frequency such as a UHF signal, a micro wave signal, and amillimeter wave signal by fixed integer values, respectively, and alsorelates to a harmonic mixer provided with transistors for mixing thesehigh-frequency signals.

[0004] 2. Description of the Prior Art

[0005]FIG. 6 is a circuit diagram of semiconductor circuitry whichconstitutes a prior art harmonic mixer as disclosed in IEEE Journal ofSolid-State Circuits Vol. 33, No. 12, December, 1998, pp. 2241, forexample. In the figure, reference numeral 1 denotes a power supplyterminal, numeral 2 a denotes a radio-frequency signal input terminal(i.e., RF input terminal) numeral 3 a denotes a local oscillation inputterminal (i.e., LO input terminal), numerals 4 a and 4 b denote outputterminals, numerals 11 and 12 denote transistors, numeral 31 denotes aconstant current source, and numerals 51 and 52 denote resistors.

[0006] The operation of the prior art semiconductor circuitry will beexplained. A DC voltage Vcc is applied to the power supply terminal 1 ofthe semiconductor circuitry. A radio-frequency signal (i.e., RF signal)input from the RF input terminal 2 a is applied to the base electrode ofthe transistor 11, and is amplified by the transistor 11. On the otherhand, a local oscillation signal (i.e., LO signal) applied to the LOinput terminal 3 a is input to the base electrode of the transistor 12,and is amplified by the transistor 12.

[0007] The constant current source 31 is connected to the emitterelectrodes of the transistors 11 and 12. Thus, an electric currenthaving a phase opposite to and an amplitude equal to those of anelectric current flowing through the transistor 11 will flow through thetransistor 12. Therefore, in the transistor 11 the RF signal of positivephase is mixed with the LO signal of negative phase and they areamplified, and in the transistor 12 the RF signal of negative phase ismixed with the LO signal of positive phase and they are amplified.

[0008] As a result, the RF signal of positive phase, the LO signal ofnegative phase, and mixture waves of the RF signal and the LO signal areoutput as a collector output of the transistor 11 by way of the outputterminal 4 a connected to the power supply terminal 1 via the resistor51. Furthermore, the RF signal of negative phase, the LO signal ofpositive phase, and mixture waves of the RF signal and the LO signal areoutput as a collector output of the transistor 12 by way of the outputterminal 4 b connected to the power supply terminal 1 via the resistor52.

[0009] The output signal of the semiconductor circuitry is defined as adifferential signal that appears between the output terminals 4 a and 4b. Thus, any (2n−1)th (n is an integer of 1 or more) harmonic having afrequency (2n−1) times as large as that of the RF signal or the LOsignal has a voltage two times as large as that of the RF signal or theLO signal while any (2n)th harmonic having a frequency 2n times as largeas that of the RF signal or the LO signal is suppressed and is thereforenot output.

[0010] When any mixture wave of the RF signal and the LO signal is notconsidered, odd-order higher harmonics of these signals can appearbetween the output terminals 4 a and 4 b. The semiconductor circuitrythus operates as a frequency multiplier for generating odd-order higherharmonics.

[0011] For the mixture of the RF signal and the LO signal, anyeven-order higher harmonic of the mixture which is an output signal of ausual fundamental harmonic mixer (e.g., a mixture wave of f_(RF)-f_(LO),where f_(RF) is the frequency of the RF signal and f_(LO) is thefrequency of the LO signal) is suppressed, and only odd-order higherharmonic of the mixture (e.g., a mixture wave of f_(RF)-2f_(LO)) appearbetween the output terminals 4 a and 4 b. The prior art semiconductorcircuitry can thus operate as a harmonic mixer for generating odd-orderhigher harmonics.

[0012] If the constant current source 31 operates ideally, neithereven-order higher harmonics of the RF signal and the LO signal noreven-order higher harmonics of the mixture of them appear between theoutput terminal 4 a and 4 b. However, when the power supply voltage Vccfrom which the semiconductor circuitry operates is as low as about 3volts, the constant current source 31 cannot be manufactured as an idealelement because the power supply voltage is low. Therefore, the constantcurrent source 31 is often replaced by a resistor of about hundreds ofohms, for example.

[0013] When the constant current source 31 does not function properly,no signal of negative phase can be generated sufficiently in each of thetransistors 11 and 12. Therefore, a problem with the prior artsemiconductor circuitry is that there causes an unbalance betweencomponents of either the LO signal or the RF signal at the outputterminal 4 a and those at the other output terminal 4 b, and thereforethe signal level of any odd-order higher harmonic falls, and thesuppression of either any even-order higher harmonic or any mixture wavesignal becomes difficult and some even-order higher harmonic signalcomponents therefore appear between the output terminals 4 a and 4 b.

[0014] To enable the semiconductor circuitry to operate from a lowervoltage, there is provided a method for combining the RF signal ofpositive phase with the LO signal of negative phase, applying thecomposite wave to the RF input terminal 2 a, combining the RF signal ofnegative phase with the LO signal of positive phase, and applying thecomposite wave to the LO input terminal 3 a, without the constantcurrent source. In this case, the semiconductor circuitry can operatefrom a lower voltage because it does not include the constant currentsource. However, since the input signal terminals for the LO signal andthe RF signal are not separated, there is a need to provide circuitseach for combining the RF signal with the LO signal wave while makingthem be out of phase by a constant phase. It is difficult to implementsuch the circuits as low-loss components included in the semiconductorcircuitry, and it is therefore necessary to implement the circuits asexternal circuits other than components included in the semiconductorcircuitry.

[0015] The above-mentioned description is directed to the case where thesemiconductor circuitry operates as a down-converter. If the RF inputterminal is replaced by an IF input terminal, the above-mentionedsemiconductor circuitry can operate as an up-converter and output an RFsignal. In this case, the output RF signal can be an odd-order harmonicof the mixture of an IF signal and an LO signal (e.g., a harmonic off_(IF)+2f_(LO), where f_(IF) is the frequency of the IF signal).

[0016] As can be understood from the above-mentioned explanation, theprior art semiconductor circuitry in which the input terminals for theRF signal and the LO signal are separately provided can suppress anyeven-order harmonic to be generated between the output terminals byusing the constant current source connected to the emitter electrodes ofthe transistors that accept the RF signal and the LO signal,respectively, and can perform a mixing of odd-order higher harmonics.Therefore, a problem with the prior art semiconductor circuitry is thatit is difficult to make the constant current source operate ideally whenthe DC voltage Vcc applied to the semiconductor circuitry is as low as 3Volts or less. And, another problem is that when the characteristics ofthe constant current source are not ideal, either any even-order higherharmonic or any mixture wave signal, particularly any even-order higherharmonic of the local oscillation signal with a large power level easilyappears between the output terminals.

SUMMARY OF THE INVENTION

[0017] The present invention is proposed to solve the above-mentionedproblems and it is therefore an object of the present invention toprovide semiconductor circuitry capable of multiplying the frequency ofa higher harmonic or mixing higher harmonics even if the semiconductorcircuitry operates from a low voltage. It is a further object of thepresent invention to provide semiconductor circuitry that can hardlygenerate even-order higher harmonics of a local oscillation signal evenif the semiconductor circuitry operates from a low voltage.

[0018] In accordance with an aspect of the present invention,semiconductor circuitry comprises a transistor pair that consists of atransistor having a base electrode to which a first signal is applied,and another transistor having a base electrode to which a signal havinga phase opposite to that of the first signal is applied, the emitterelectrodes of the transistors being connected to each other and thecollector electrodes of the transistors being connected to each other, afurther transistor connected between a common emitter of the transistorpair and a first fixed voltage level and having a base electrode towhich a second signal is applied, an output load connected between acommon collector of the transistor pair and a second fixed voltagelevel, and an output circuit for furnishing a third signal from thecommon collector of the transistor pair.

[0019] In accordance with another aspect of the present invention, thesemiconductor circuitry can include two semiconductor circuits accordingto the first aspect of the present invention. In this case, the secondsignal of positive phase is applied to one of the two semiconductorcircuits while the second signal of negative phase is applied to theother one of them. The former semiconductor circuit outputs the thirdsignal of positive phase while the latter semiconductor circuit outputsthe third signal of negative phase.

[0020] The above-mentioned transistors can be FETs. In this case, thebase electrode, emitter electrode, and collector electrode of eachtransistor correspond to a gate electrode, a source electrode, and adrain electrode of a corresponding FET, respectively. The emitter orsource electrode of the transistor that accepts the second signal isdirectly connected to the first fixed voltage level, or is alternativelyconnected to the first fixed voltage level by way of another circuitelement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a circuit diagram showing the structure of semiconductorcircuitry according to a first embodiment of the present invention;

[0022]FIG. 2 is a circuit diagram showing the structure of semiconductorcircuitry according to a variant of the first embodiment;

[0023]FIG. 3 is a circuit diagram showing the structure of semiconductorcircuitry according to a second embodiment of the present invention;

[0024]FIG. 4 is a circuit diagram showing the structure of semiconductorcircuitry according to a third embodiment of the present invention;

[0025]FIG. 5 is a circuit diagram showing the structure of semiconductorcircuitry according to a fourth embodiment of the present invention; and

[0026]FIG. 6 is a circuit diagram showing the structure of a prior artharmonic mixer circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Embodiment 1

[0028]FIG. 1 is a circuit diagram showing the structure of semiconductorcircuitry according to a first embodiment of the present invention. Inthe figure, reference numeral 1 denotes a power supply terminal, numeral2 a denotes a radio-frequency signal input terminal (RF input terminal),numeral 3 a denotes a local oscillation input terminal (LO inputterminal), numeral 4 a denotes an output terminal, numerals 11 to 13denote transistors, and numeral 51 denotes a resistor.

[0029] The transistors 11 and 12 constitute a transistor pair having acommon emitter N1 including the emitter electrodes of the transistorsconnected to each other and a common collector N2 including thecollector electrodes of the transistors connected to each other. Thecommon emitter N1 is connected to the collector electrode of the othertransistor 13 having an emitter electrode grounded, and the commoncollector N2 is connected to the output terminal 4 a, and is alsoconnected to the power supply terminal 1 by way of the resistor 51disposed as an output load. Therefore, a DC voltage (Vcc) applied to thepower supply terminal 1 is supplied to each of the transistors 11 to 13by way of the resistor 51. Furthermore, the RF input terminal 2 a isconnected to the base electrode of the transistor 13, and the LO inputterminals 3 a and 3 b are connected to the base electrodes of thetransistors 11 and 12, respectively.

[0030] A description will be made as to the operation of thesemiconductor circuitry of the first embodiment. An RF signal applied tothe RF input terminal 2 a is input to the base electrode of thetransistor 13 and is amplified by the transistor 13. Furthermore, an LOsignal of positive phase applied to the LO input terminal 3 a is inputto the base electrode of the transistor 11 and is amplified by thetransistor 11, and the LO signal of negative phase applied to the LOinput terminal 3 b is input to the base electrode of the transistor 12and is amplified by the transistor 12. The other transistor 13 thatamplifies the RF signal is connected to the emitter electrodes of thetransistors 11 and 12. Therefore, mixture waves of the LO signal ofpositive phase and the RF signal of positive phase and higher harmonicsof the LO signal of positive phase appear at the collector electrode ofthe transistor 11. Furthermore, mixture waves of the LO signal ofnegative phase and the RF signal of negative phase and higher harmonicsof the LO signal of negative phase appear at the collector electrode ofthe transistor 12.

[0031] Any pair of mixture waves (e.g., a pair of mixture waves having afrequency of f_(RF)-f_(LO)) respectively generated by the transistors 11and 12 with a fundamental harmonic mixing has mixtures waves which are180°out of phase with each other at the output terminal 4 a. Therefore,such pairs of mixture waves are counterbalanced and hence are not outputvia the output terminal 4 a. Furthermore, no even-order higher harmonicof the LO signal (whose frequency is 2nf_(LO), where n is an integer of1 or more) is output and no mixture wave of an odd-order higher harmonicof the LO signal and a higher harmonic of the RF signal (whose frequencyis (2n−1)f_(LO)±mf_(RF), where m is an integer of 1 or more) is outputbecause any pair of even-order higher harmonics of the LO signalgenerated by the transistors 11 and 12 has even-order higher harmonicswhich are 180°out of phase with each other and any pair of mixture wavesof an odd-order higher harmonic of the LO signal and a higher harmonicof the RF signal generated by the transistors 11 and 12 has mixturewaves which are 180°out of phase with each other. As a result, onlyhigher harmonics of frequencies mf_(RF) of the RF signal, odd-orderhigher harmonics of frequencies (2n−1)f_(LO) of the LO signal, andmixture waves of frequencies (2nf_(LO)±mf_(RF)) of an even-order higherharmonic of the LO signal and a higher harmonic of the RF signal, whichare generated by the transistors 11 and 12, are output via the outputterminal. The semiconductor circuitry of the first embodiment thusoperates as a harmonic mixer.

[0032] The semiconductor mixer circuitry of the first embodiment canoperate from a relatively-low voltage power supply of 3 Volts or lessbecause the semiconductor mixer circuitry does not need any constantcurrent source. Furthermore, although the emitter electrode of thetransistor 13 is grounded, to expand the dynamic range of the RF signalit is possible to insert either a resistor or an inductor between theemitter electrode of the transistor 13 and the ground potential.

[0033] The semiconductor circuit needs two signals of positive phase andof negative phase for the LO signal. When only one of them is given tothe semiconductor circuitry, a balun circuit only has to be connected tothe former stage of the semiconductor mixer circuitry. For example, thetwo signals of positive phase and of negative phase can be generated byusing such a circuit as a differential amplifier or a circuit thatemploys a transistor pair consists of a common base transistor andeither a common emitter transistor or a common collector transistor.Therefore, in accordance with the first embodiment, there is providedsemiconductor mixer circuitry that can operate from a relatively-lowvoltage which is about 2 to 3 Volts.

[0034] The above-mentioned description is directed to the case where thesemiconductor circuitry of the first embodiment operates as adown-converter. If the RF input terminal is replaced by an IF inputterminal, the above-mentioned semiconductor circuitry can operate as anup-converter and output an RF signal. In this case, the output RF signalcan be a mixture wave of an even-order higher harmonic of an LO signaland a higher harmonic of an IF signal (whose frequency is2nf_(LO)±mf_(IF)).

[0035] When the semiconductor circuitry is used as either anup-converter or a down-converter, the LO signal input to the LO inputterminals 3 a and 3 b has to satisfy the following given condition:f_(RF)=2nf_(LO).

[0036] Although the above description is directed to the case where thesemiconductor circuitry operates as a mixer circuit, the semiconductorcircuit can be made to operate as a frequency multiplier. For example,when a signal of positive phase is input to the input terminal 3 a andthe signal of negative phase is input to the other input terminal 3 b,an odd-order higher harmonic of the input signal is output via theoutput terminal 4 a. At this time, a DC signal is input to the inputterminal 2 a. As an alternative, it is possible to apply a signal otherthan the DC signal to the input terminal 2 a by disposing a circuit thatperforms impedance matching only to a desired multiplication wavegenerated from the input signal at the output of the semiconductorcircuitry.

[0037] The above description of the semiconductor circuitry of the firstembodiment is directed to the case where junction bipolar transistorsare used as the transistors 11 to 13. As an alternative, FETs can beused as the transistors 11 to 13. FIG. 2 is a circuit diagram showing avariant of the semiconductor circuitry, which is constructed by usingFETs as the transistors of FIG. 1. In this case, the collectorelectrode, emitter electrode and base electrode of each junction bipolartransistor are replaced by a drain electrode, a source electrode and agate electrode of a corresponding FET in the above description of theoperation of the semiconductor circuit, and the same advantages areprovided. The FETs used as the transistors 11 to 13 can be GaAsFETs orMOS-FETs.

[0038] Embodiment 2

[0039]FIG. 3 is a circuit diagram showing the structure of semiconductorcircuitry according to a second embodiment of the present invention. Inthe figure, reference numeral 61 denotes a capacitor. Compared with thesemiconductor mixer circuitry of the above-mentioned first embodimentshown in FIG. 1, the semiconductor mixer circuitry according to thesecond embodiment differs from the semiconductor mixer circuitry of thefirst embodiment in that the capacitor 61 is connected in parallel to aresistor 51. The same components as shown in FIG. 1 are designated bythe same reference numerals, and therefore the description of thosecomponents will be omitted hereafter.

[0040] When the semiconductor mixer circuitry is made to operate as adown-converter, if the capacitor 61 is assumed to be short-circuited forthe frequencies of an RF signal and an LO signal, and to have animpedance of the order of the resistance of the resistor 51 for thefrequency of an IF signal, the RF signal, the LO signal, and anyodd-order higher harmonic of the LO signal are suppressed by thecapacitor 61 and are therefore not output via an output terminal.Therefore, the semiconductor mixer circuitry offers an advantage in thatit can suppress spurious components at the output terminal 4 a, and itcan therefore simplify the structure of a spurious suppression filterexternally connected to the semiconductor mixer circuitry. Furthermore,since the semiconductor mixer circuitry can suppress the spuriouscomponents within the mixer circuitry, it can improve the efficiency ofconversion of the input signals to a desired wave.

[0041] The above description of the semiconductor circuitry of thesecond embodiment is directed to the case where junction bipolartransistors are used as the transistors 11 to 13. As an alternative,FETs can be used as the transistors 11 to 13, as previously mentioned inEmbodiment 1. In addition, the semiconductor circuitry of the secondembodiment can be made to operate as a frequency multiplier, like thatof the above-mentioned first embodiment.

[0042] Embodiment 3

[0043]FIG. 4 is a circuit diagram showing the structure of semiconductorcircuitry according to a third embodiment of the present invention. Inthe figure, reference numeral 5 a denotes an IF input terminal, andnumeral 71 denotes an inductor. Compared with the semiconductor mixercircuitry of the above-mentioned first embodiment shown in FIG. 1, thesemiconductor mixer circuitry according to the third embodiment differsfrom the semiconductor mixer circuitry of the above-mentioned firstembodiment in that the RF input terminal 2 a is replaced by the IF inputterminal 5 a and the resistor 51 is replaced by the inductor 71. Theinductor 71 can be implemented as a spiral inductor or the like formedon the semiconductor substrate. The same components as shown in FIG. 1are designated by the same reference numerals, and therefore thedescription of those components will be omitted hereafter.

[0044] When the semiconductor mixer circuitry is made to operate as adown-converter, if the inductor 71 is assumed to be short-circuited forthe frequencies of an IF signal and an LO signal, and to have animpedance of the order of the resistance of the resistor 51 as shown inFIG. 1 for the frequency (e.g., f_(IF)+2f_(LO)) of an RF signal, the IFsignal and the LO signal are suppressed by the inductor 71 and aretherefore not output via an output terminal. Therefore, thesemiconductor mixer circuitry offers an advantage in that it cansuppress spurious components at the output terminal 4 a, and it cantherefore simplify the structure of a spurious suppression filterexternally connected to the semiconductor mixer circuitry. Furthermore,since the semiconductor mixer circuitry can suppress the spuriouscomponents within the mixer circuitry, it can improve the efficiency ofconversion of the input signals to a desired wave. In addition, sincethe voltage drop caused by the resistor 51 is eliminated by using theinductor in place of the resistor, it is possible to make thesemiconductor circuitry operate from a lower voltage compared with thoseof the first and second embodiments.

[0045] The above description of the semiconductor circuitry of the thirdembodiment is directed to the case where junction bipolar transistorsare used as the transistors 11 to 13. As an alternative, FETs can beused as the transistors 11 to 13, as previously mentioned inEmbodiment 1. The semiconductor circuitry of the third embodiment can bemade to operate as a frequency multiplier, like that of theabove-mentioned first embodiment.

[0046] Embodiment 4

[0047]FIG. 5 is a circuit diagram showing the structure of semiconductorcircuitry according to a fourth embodiment of the present invention. Inthe figure, reference numeral 2 b denotes an RF input terminal foraccepting an RF signal of negative phase, 4 b denotes an output terminalthat pairs up with an output terminal 4 a, for outputting a differentialsignal, numerals 14 to 16 denote transistors, and numeral 52 denotes aresistor. The same components as shown in FIG. 1 are designated by thesame reference numerals, and therefore the description of thosecomponents will be omitted hereafter.

[0048] The semiconductor mixer circuitry of the fourth embodiment hastwo semiconductor mixer circuits of FIG. 1 in parallel. The firstsemiconductor mixer circuit is constructed of a first transistor pairconsists of transistors 11 and 12, a transistor 13, and a resistor 51.In the same way, the second semiconductor mixer circuit is constructedof a second transistor pair consists of the transistors 14 and 15, thetransistor 16, and the resistor 52.

[0049] A signal having a phase opposite to that of an LO signal appliedto an LO input terminal 3 a is input to an LO input terminal 3 b.Furthermore, a signal having a phase opposite to that of an RF signalapplied to an RF input terminal 2 a is input to the RF input terminal 2b. And, an output signal is furnished as a differential signal thatappear between the output terminal 4 a of the first semiconductor mixercircuit and the output terminal 4 b of the second semiconductor mixercircuit.

[0050] Compared with the semiconductor mixer circuitry of theabove-mentioned first embodiment, the semiconductor mixer circuitry ofthe fourth embodiment having such a balance type structure can suppressany odd-order higher harmonic of the RF signal and any mixture wave ofan even-order higher harmonic of the LO signal and an even-order higherharmonic of the RF signal, which are furnished to the output terminals.Therefore, the semiconductor mixer circuitry can easily output a mixturewave of a second harmonic of the LO signal and a first harmonic of theRF signal, which is the most general output signal from a generalharmonic mixer. The semiconductor mixer circuitry thus offers anadvantage in that since it can suppress many spurious components, it cantherefore simplify the structure of a spurious suppression filterconnected to the output terminals of the semiconductor mixer circuitry.

[0051] The above-mentioned description is directed to the case where thesemiconductor circuitry of the fourth embodiment operates as adown-converter. If the RF input terminals is replaced by IF inputterminals, the above-mentioned semiconductor circuitry can be made tooperate as an up-converter and output an RF signal. In this case, theoutput RF signal can be a mixture wave of an even-order harmonic of theLO signal and an IF signal.

[0052] The above description of the semiconductor circuitry of thefourth embodiment is directed to the case where junction bipolartransistors are used as the transistors 11 to 13. As an alternative,FETs can be used as the transistors 11 to 13, as previously mentioned inEmbodiment 1. In this case, the collector electrode, emitter electrodeand base electrode of each junction bipolar transistor are replaced by adrain electrode, a source electrode and a gate electrode of acorresponding FET in the above description of the operation of thesemiconductor circuit, and the same advantages are provided.Furthermore, the semiconductor circuitry of the fourth embodiment can bemade to operate as a frequency multiplier, like that of theabove-mentioned first embodiment.

[0053] Furthermore, although the above description is directed to thecase where two semiconductor mixer circuits of FIG. 1 are connected inparallel to each other and hence constitutes balance type semiconductorcircuitry, the semiconductor circuitry of the fourth embodiment can bealternatively constructed of two semiconductor mixer circuits of FIG. 2or 3 connected in parallel to each other. This variant offers the sameadvantages.

What is claimed is:
 1. Semiconductor circuitry comprising: a transistorpair that consists of a first transistor having a base electrode towhich a first signal is applied, and a second transistor having a baseelectrode to which a signal having a phase opposite to that of the firstsignal is applied, emitter electrodes of said first and secondtransistors being connected to each other and collector electrodes ofsaid first and second transistors being connected to each other; a thirdtransistor having a base electrode to which a second signal is applied,an emitter electrode connected to a first fixed voltage level, and acollector electrode connected to a common emitter of said transistorpair; and an output circuit for connecting a common collector of saidtransistor pair to a second fixed voltage level by way of an outputload, and for furnishing a third signal from the common collector ofsaid transistor pair.
 2. The semiconductor mixer circuitry according toclaim 1 , wherein said output load consists of a resistor and acapacitor in parallel.
 3. The semiconductor mixer circuit according toclaim 1 , wherein said output load consists of an inductor. 4.Semiconductor circuitry comprising: a first transistor pair thatconsists of a first transistor having a base electrode to which a firstsignal is applied, and a second transistor having a base electrode towhich a signal having a phase opposite to that of the first signal isapplied, emitter electrodes of said first and second transistors beingconnected to each other and collector electrodes of said first andsecond transistors being connected to each other; a third transistorhaving a base electrode to which a second signal is applied, an emitterelectrode connected to a first fixed voltage level, and a collectorelectrode connected to a common emitter of said first transistor pair; afirst output circuit for connecting a common collector of said firsttransistor pair to a second fixed voltage level by way of an outputload, and for furnishing a third signal from the common collector ofsaid first transistor pair; a second transistor pair that consists of afourth transistor having a base electrode to which the first signal isapplied, and a fifth transistor having a base electrode to which thesignal having a phase opposite to that of the first signal is applied,emitter electrodes of said fourth and fifth transistors being connectedto each other and collector electrodes of said fourth and fifthtransistors being connected to each other; a sixth transistor having abase electrode to which the second signal is applied, an emitterelectrode connected to the first fixed voltage level, and a collectorelectrode connected to a common emitter of said second transistor pair;and a second output circuit for connecting a common collector of saidsecond transistor pair to the second fixed voltage level by way of anoutput load, and for furnishing a signal having a phase opposite to thatof the third signal from the common collector of said second transistorpair.
 5. Semiconductor circuitry comprising: a transistor pair thatconsists of a first FET having a gate electrode to which a first signalis applied, and a second FET having a gate electrode to which a signalhaving a phase opposite to that of the first signal is applied, sourceelectrodes of said first and second FETs being connected to each otherand drain electrodes of said first and second FETs being connected toeach other; a third transistor having a gate electrode to which a secondsignal is applied, a source electrode connected to a first fixed voltagelevel, and a drain electrode connected to a common source of saidtransistor pair; and an output circuit for connecting a common drain ofsaid transistor pair to a second fixed voltage level by way of an outputload, and for furnishing a third signal from the common drain of saidtransistor pair.